1. Field of the Invention
The present invention relates to a connection structure for a shield wire, where a shield conductor of the shield wire is fastened tightly by a shield fastening portion for connection.
2. Description of the Related Art
Patent Literature 1 (Japanese Patent Application Laid-Open Publication No. 2010-49859) discloses a shield connector which employs a conventional connection structure for a shield wire. As shown in FIG. 1, a shield connector 50 includes an inner housing 51, a connection terminal 52 which the inner housing 51 accommodates, and a shield shell 60 which covers the outer circumference of the inner housing 51.
The inner housing 51 is formed of an insulator which has a predetermined permittivity. The connection terminal 52 includes a core wire fastening portion 53 and a contact portion 54 which is for a connection to a corresponding terminal. The shield shell 60 is formed of a conductive material. The shield shell 60 includes a shield body 61 which covers the inner housing 51, a shield fastening portion 62 which protrudes backward from the shield body 61, and a wire fastening portion 63. The shield fastening portion 62 is provided with a plurality of holes 64.
A coaxial shield wire W1 includes a core wire 70 which is a conductor, an insulating inner cover 71 which covers the outer circumference of the core wire 70, a braided wire 72 which is a shield conductor and covers the insulating inner cover 71, and an insulating outer cover 73 which covers the outer circumference of the braided wire 72. At a terminal part of the shield wire W1, the core wire 70 is exposed and then the braided wire 72 is exposed. The core wire 70 is fastened tightly by the core wire fastening portion 53 of the connection terminal 52 for a connection thereto. The braided wire 72 is fastened tightly by the shield fastening portion 62 of the shield shell 60 for a connection thereto. The shield wire W1 is fastened tightly from the top of the insulating outer cover 73 by the wire fastening portion 63 of the shield shell 60 and firmly fixed thereto.
As shown in FIG. 2A, in order to enhance the wire fastening force at the shield fastening portion 62, there is a need to fasten the braided wire 72 tightly with a strong fastening force. As shown in FIG. 2B, if the strong fastening force is applied on the shield fastening portion 62, the insulating inner cover 71 is extremely compressed so that the core wire 70 might snap. There is therefore a limit of the fastening force to be applied on the shield fastening portion 62.
The exposed braided wire 72 is also easy to fray. There is therefore a need to prevent the fray of the braided wire 72.
Then, in order to achieve the enhancement of the wire fastening force at the shield fastening portion 62 and the prevention of the fray of the braided wire 72 without having the core wire 70 snap, the shield fastening portion 62 has the following structure.
That is, as shown in FIGS. 3 and 4, the shield fastening portion 62 is provided with a plurality of holes 64. The shield fastening portion 62 also has a conductor connection surface made as a knurled surface 65 by knurling.
As shown in FIG. 4, in the above-described structure, since the braided wire 72 receives the compression force by being fastened at the shield fastening portion 62, the braided wire 72 is pressed into each of the holes 64 of the shield fastening portion 62. The edge effect of each of the holes 64 enables to obtain the wire fastening force (wire pulling strength) which is at a predetermined level or more, even though the strong fastening force is not applied on the shield fastening portion 62. Also, a concave-convex surface by knurling prevents the fray of the braided wire 72.
However, in the above-described conventional example, as shown in FIG. 4, when a concave part 65a of the knurled surface 65 is positioned around each of the holes 64, the substantial amount of pressing the braided wire 72 into the hole 64 (engagement amount of the braided wire 72) decreases, and thereby the edge effect by the hole 64 diminishes. It is therefore not possible to surely prevent the fray of the braided wire 72 and also enhance the wire fastening force (wire pulling strength) at the shield fastening portion 62.